

// call apply


var pet={
    words:"...",
    speek:function(say){
        console.log(say+"  "+this.words)
    }
}

// this指向 pet
pet.speek('speak');

var dog={
    words:"wang wang wang"
}
// 通过call ，改变了上下文 ，将this指向dog 
pet.speek.call(dog,'speak')

// this指向 pet
pet.speek('speak');